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Technology Day
11th May 2009
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TECHNOLOGICAL TOOLS
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Power Sector Western Region
Use of Electrical Torque wrench for Tightening
Boiler Structure Bolts
At 1 x 500 MW Khaperkheda
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Cycle time reduction in tightening boiler structure bolts
Background
At boiler erection site thousands of BOLTED JOINTS are to be tightened
MANUALLY using DE Spanners for snug tightening & Torque tighteningby trip torque type long handle torque spanner.
The process of bolting arrangement consumes enormous time forachieving desired results, including uniform tightening & ensuring adesigned torque value.
This process was identified for taking up Improvement project because ofthe following
being repetitive in nature
time consuming
labour intensive
having substantial amount of preparatory work to be done before thestarting actual process (set up time)
high level of risk involved (some locations for actual work place areabove 80 meter above ground level & are to be performed ontemporarily erected scaffoldings
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Objective
Reduction in time taken for complete bolting arrangementnecessary for a 500 MW Boiler erection (at Khaperkheda siteabout 40, 000 no. M24 Bolts of lengths 70160 mm are used)
Ensuring designed tightness of bolting arrangement without
further need of cross checking by Quality representative Safer working conditions for Operator
Cycle time reduction in tightening boiler structure bolts
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Evaluation of alternatives
1. Pneumatic torque wrench Benefits
Available with leading hand tool manufacturers like Bosch, Ingersoll Rand &
others.
Widely used in manufacturing plants (automotive assembly lines) where high
turnover per day is the hour of need (but here the Operator has a fixed place &jobs move to his operating area one after another).
These wrenches are comparatively lighter.
Drawbacks for us
Difficulties in ensuring dry air to the wrench in all weather conditions
Maintaining desired air pressure at a long distance through a compressor
Requirement of supports since length of air pipes may extend up to 100 meters
Thus making the whole arrangement very clumsy & big.
Cycle time reduction in tightening boiler structure bolts
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Evaluation of alternatives
2. Hydraulic torque wrench
Benefits
Available with leading hand tool manufacturers
Widely used in manufacturing plants
Drawbacks for us
Need sophisticated hydraulic equipment (difficult to maintain)
Require very good quality pressure hoses to feed optimumliquid pressure to the wrench limiting factors
Practically impossible to provide such facilities at sites
Cycle time reduction in tightening boiler structure bolts
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Evaluation of alternatives
3. Electrically operated torque wrench
Benefits
Such wrenches are popular in assembly lines especially where
job sizes are bigger & operator has to move around the job Available with leading hand tool manufacturers
Electrical cables are much smaller, lighter & easily
maneuverable
Operate at 1 phase ac supply abundantly available at all areasof sites
Cycle time reduction in tightening boiler structure bolts
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Electrically operated torque wrench(contd..)
Results of Field Trial
M/s Tristar Industrial Tools Pvt limited was a source located for
making a demo at Khaperkheda
Trial was successfully done on 10thApril 2009 at a height of about
10 meters on Column number 19.
Time taken to fully tighten bolted joint by ETW was about 15
seconds as against 3 to 4 minutes by a handle type Trip Torque
Wrench
Substantial saving in operation time for the activity
Saving in manual effort by Operator
Positive assurance of Quality of bolted joint.
Cycle time reduction in tightening boiler structure bolts
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Electric wrench for tightening boiler structure bolts
Technische Daten DEATechnical data DEA
PLARADGERMANY MakeTechnische Daten DEATechnical data DEA
Our select ion
Type DEA 12 TLX Torqu e 200 1220 NM Weigh t 6,8 kg
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Electr ic wrench tightening of boiler structure bolts
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Electr ic wrench tightening of boiler structure bolts
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Expected Benefits
Tangible Saving in Time - On average saving of about 3 minutes per bolt
Saving in manpower cost
No need for Quality representative to ensure desired objectiveof proper tightness
Additional helper to hold spanner and a trip torque wrench, notrequired.
Intangible
Safety of Operating Personnel (Operators & others assisting him)
from any Accidental fall due to Slipping Slipping / Falling of the job from temporary scaffolding
Better safety of personnel on ground from falling of long torquewrench etc.
Cycle time reduction in tightening boiler structure bolts
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Measurement of Face Run- out of IP & LP Rotors
by improvised technique at site
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Measurement of Face Run- out of I P & LP Rotors
Normal Practice (Contd..)
The normal method has few problems associated with it1. It is not possible to restrict axial movement of the rotor in order to avoid
overshooting the range of the dial gauge.
2. Area of contact being very small, it requires extreme care and controlwhile operating the EOT, lest it should cause an irreparable accident and
lead to loss to both men and material.3. It has often been noticed that there is quite an error between the
measurement made at shop and those made at site leading to avoidableloss of time in correspondence, summoning experts from MUs, etc.
4. It gives the feeling of using a very primitive and un-reliable method of
measurement.5. Overall, it is never like measuring the run-outs by anchoring the rotor on
a lathe to take the measurements and thats exactly the cause of theerror.
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Measurement of Face Run- out of I P & LP Rotors
Suggested New Method
A simple device is made at site using the following material
Shaft of 40mm x 1000mm long 1 no.
Ball Bearings with Plummer block for above shaft 2 nos.
Supports to anchor the Plummer blocks 2 nos.
Cross arm 1 no.
Dial Gauges for mounting to X-arm 2 nos.
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Measurement of Face Run- out of I P & LP Rotors
Brg with
Plummer
Block
Cross Arm
Shaft Support provided by UnitExternal Support for
anchoring the
Plummer Block
Dial
Pointers
Dia
40
Shaft
Fixture developed and used
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Measurement of Face Run- out of I P & LP Rotors
Advantages
User friendly and costs only Rs.5000/- to make.
Does not require too much of a precision in machiningthe shaft.
Does away with repeated rotation of the rotor forevery reading.
Reduces the risk of the rotor toppling during rotationby EOT crane.
Compares well with the values attained at works on alathe.
Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
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Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
TATA Trombay
This was the 1sttimethe Generator Statorhas been lifted by
Strand Jack Methodin PS-WR. Also, thisis the 1st for 250MWStators in the whole
of BHEL. Pictureshows Stator liftedoff the Blocks.
Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
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Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
TATA Trombay.Contd
Stator lifting inprogress
Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
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Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
TATA Trombay.Contd
Stator lifted andbeing moved insidethe A-Row of TG
Building
Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
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Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
TATA Trombay.Contd
Stator lifted abovethe bottom of TGDeck and ready to
be moved inside forplacement.
Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
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Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8
TATA Trombay.Contd
Picture shows theStrand JackHydraulic Control
System
Stator l i f ting by Strand Jack Method at 1x250MW Uni t#8
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Stator li f ting by Strand Jack Method at 1x250MW Uni t#8
TATA Trombay.Contd
Picture shows statorin position
The entire operation
was completed in 4hrs from the start.
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PORTABLE INDUCTION HEATING MACHINE
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I NDUCTION HEATING MACHINE
Conventionally, we at BHEL Power Sector Sites have been using theInduction Heating Machines of EDN Bangalore make. There are certain
disadvantages of using this equipment listed below:1. Too bulky and comes in two parts one the Induction HeatingEquipment proper and the other, the operators panel. Weighs a fewtonnes.
2. Due to its bulk, moving the machine to different areas of work is an
arduous task. Each shift of the machine is a 1 days activity.3. Often, it has been seen that when the machine is moved from onelocation to the other is has not been in use for a few months, the next re-start is faced with quite a few problems. The reason is not known.
4. Getting spares on time for the equipment is a big issue. This results in
machines with minor repairs and requiring spares quarantined.5. Overall the machine is not user-friendly
6. Costs around Rs. 75 Lakhs per machine
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I nduction Heating Machine -.Contd
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I nduction Heating Machine -.Contd
Alternatively, there are machines available in the market and beingused by our competitors that is a vast improvement on the EDN
Make machine and has the following advantages:1. Very small and easily portable, thus rendering easy movementof the machines to various locations without loss of vital erectioncycle time. Requires only a 2-3 hrs for shifting and re-connecting.The entire machine is as compact as welding transformer and issingle modular. Weighs approx. 105Kgs.
2. The connections are very simple and does not need expertise.
3. Though imported, has a presence in the Indian market for thelast 3 years and has been used to weld pipes of 94mm thick atSipat. The machine can be used to thicknesses in excess of100mm pipes as well. The size of MS Pipe for the proposed 660MWUnit with Full Flow is 660 x 102mm.
4. Costs only Rs.30 Lakhs. For every one machine of EDN Make,one can two of this kind.
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I nduction Heating Machine -.Contd
C d
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I nduction Heating Machine -.Contd
660 MW 800 MW
System Material Size Material Size
MS - HalfFlow
P91 OD 508 x 80 P91 ID 370 x 66
MSFullFlow
P91 OD 660 x 102 P91 ID 480 x 90
HP BypassU/S
P91 OD 355.6 x 52 P91 OD 355.6 x 54
HRHHalfFlow
P91 OD 711 x 40 P91 OD 813 x 49
HRHFull
Flow
P91 OD 864x48 P91 OD 1016 x 58
LP BypassU/S & D/S
P91 OD 711 x 40 /OD 1219 x10(SA691 2 Cr)
P91 OD 864 x 50 /OD 965 x 35
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Induction Heating for Opening & Tightening
Casing fasteners of Steam Turbine
I nduction Heating for opening & tightening
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I nduction Heating for opening & tighteningCasing of Steam Turbine
Introduction
Casing of steam turbines are tightened together by usingthreaded fasteners of M48 to M140 size .
These fasteners referred commonly as studs and cap nuts have
to be tightened firmly to withstand the high internal pressure
and temperature.
During the tightening process, specified value of elongation has
to be achieved so that during working at high temperature, the
nuts will not slacken .
A recommended practice for tightening these fasteners is heat
tightening.
I nduction Heating for opening & tightening
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I nduction Heating for opening & tighteningCasing of Steam Turbine
Commonly used devices for heating the fasteners
Electric heaters - which include heater elements, cables, power source
/transformer of high capacity etc.
Gas heaters. This is relatively simpler method which uses the specially
fabricated bolt heating devices - Gas Torches with special nozzles, and
oxy-acetylene cylinders , compressed air supply etc.
Main disadvantages of the above two methods
Long time taken for the operation
Due to the slower rate of heating, effectiveness of these methods is
less and some other problems such as seizure of the threads also
occur quite frequently.
Apart from this, the arrangements required are also complex and timewasted in maintenance / repairs of the equipment in case of defects is
quite considerable.
I nduction Heating for opening & tightening
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I nduction Heating for opening & tighteningCasing of Steam Turbine
Induction heating method for threaded fasteners
Induction heating method is being used in other site applications such
as preheating of joints for special welding of alloy steel pipe lines inthermal power stations.
This method is very quick and effective means for heating.
By using some modified gadgets, it was found suitable for loosening
and tightening of the big size threaded fasteners of steam turbines,
valves etc.
SAS Nagpur decided to use the induction heating method for loosening
and tightening of threaded fasteners.
This method has resulted in saving valuable time for dismantling and
assembly of steam turbines during overhauls. The method is simple
and highly effective.
With the use of induction heating method, the problem of seizure of
threads necessitating cutting and gouging of the nuts and studs, in
LMW design, has been minimized.
I nduction Heating for opening & tightening
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I nduction Heating for opening & tighteningCasing of Steam Turbine
Comparison of time required for bolt opening
210 MW /500 MW KWU Electric/ Gas Heating Induction Heating
HP inner casing 6 hrs 3 hrs
IP Outer casing 10 hrs 7 hrs
IP inner casing 14 hrs 8 hrs
Time saved for overhauling is 3 days .
For a 210 MW set this translates into a gain of 5.04 million units perday
i.e approx. Rs. 2 crore per day
For 500 mw set, 12 million units per day i.e.approx. Rs.4.8 crore perday
LASER ALIGNMENT KIT
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LASER ALIGNMENT KIT
OBJECTIVETo carry out various alignment works in Turbine erection
With high precision.
At a reduced cycle time.
WORKS CARRIED OUT
Catenary of pedestals
Centering of bores of Diaphragms, Pedestals, Shaft Seals etc. Alignment of Rotors.
CATENARY OF PEDESTALS
Accuracy of 10 Microns achievable.
Source equipments to be placed at extreme pedestals.
Mobile equipment placed in intermediate pedestals.
Laser is passed thro mobile equipment and adjustments carried
out as per requirement.
LASER ALIGNMENT KIT
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LASER ALIGNMENT KIT
Centering of Bores of diaphragms,pedestals,shaft seals etc
Source Laser device fixed in one extreme end pedestalReceiver end device fixed in other extreme pedestal.
Special fixtures used for centering of intermediate pedestals.
Online adjustment possible.
Alignment of Rotors
Can cater to Coupling Dia from 100 mm to 1200 mm.Alignment Device fixed on couplings to be aligned
Total misalignment is indicated by just 60 degree rotation of Rotors.
Misalignment values as well as correction required indicated in
display.
Salient Advantages
Saving in Cycle time.
Accuracy of Measurement.
Indication of correction factors.
LASER ALIGNMENT KIT
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LASER ALIGNMENT KIT
CONCLUSION
The Laser Alignment kit is a useful equipment that is State of the Art
in Technology and can be used very effectively in Turbine activities at
high precision and reduced cycle time, as has been proved in
Kudankulam site.
Hence extensive use of this equipment has to be practiced.
ORBITAL WELDING
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ORBITAL WELDING
PurposeTo provide leak proof joint between Tube to tube sheetin Condenser in addition to Forced expansion
ProcessGTAW without filler wire addition
SIGNIFIC NT SPECTS
Material-Titanium
Large Qty of welding
Welding in position & at site
Materialsupply by Russians
TIT NIUM TUBES
Grade : ASTM B 338 Gr2
Tube Sheet : 35 + 5 mm thick
Material : ASTM A516Gr 70 + ASTMB 265 Gr 1 CLAD
ORBITAL WELDING
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ORBITAL WELDING
Why Titanium is used?
Provides excellent resistance to general and localized attack under
most oxidizing, neutral and inhibited reducing conditions inaqueous environments.
Corrosion Resistance due to stable, protective strongly adherentoxide film which forms instantly when a fresh surface is exposedto air moisture.
This film is transparent and not deducted by visual means.
Titanium resist corrosion by sea water to temperature as high as260 0C.
Even exposed to sea water for many years at a depth of over a mileshows no measurable corrosion.
Provides over 25 years of trouble free sea water service forchemical refinery de-salination and nuclear industries
ORBITAL WELDING
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ORBITAL WELDING
Has the ability to resist erosion by high velocity sea water
The presence of abrasive particles such as sand has only a small
effect on the corrosion resistance of Titanium
Production began in the late 1950s
Most widely used titanium is commercial pure (99.5 % Ti)
Manufacturing Process
Ingot slab Hot strip cold strip Slitting Forming TIG
Welding Stress relieving Eddy Current & Ultrasonic testing
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Tensile, flare, flattening & reverse flattening
Visual InspectionCleanliness, ID, OD, Surface condition, end condition
and marking.
Tube to tube sheet joiningContact Rolling (0 to 5 % wall thinning for a length of 10
mm)
Orbital WeldingFor highly reliable leak tightness
Forced Rolling (8 to 10 % wall thinning for a length of
25mm)
Physical Testing
ORBITAL WELDING
PROCESS FLOW CHART
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PROCESS FLOW CHART
Front / Rear end tube sheet cleaningwire
brush mounted in portable drilling machine
followed by acetone
Visual inspection
Titanium tube insertion
Initial cleaning before contact rolling
Initial contact rolling up to 10mm
Sh 1 of 3
PROCESS FLOW CHART CONTD
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End facing of tube & tube sheet up to 0.05 mm
Welding
Visual inspection
Rectification of repair work
Final expansion 8 to 10 % by lubricating
SAE 40 oil
Excess length trimming in the rear side
PROCESS FLOW CHART CONTDSh 2 of 3
PROCESS FLOW CHART CONTD Sh 3 f 3
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Tube tightness test by MAUS Gun G-150
Dye Penetrant testing
Final cleaning by acetone
PROCESS FLOW CHART CONTD Sh 3 of 3
TUBE SPECIFICATION
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TUBESPECIFICATION
TUBE INSERTION AT KODAMKULAM
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TUBE INSERTION AT KODAMKULAM
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FRONIUS MODEL - FPA 2000 (AUSTRIAN MAKE)
PROGR M BLE ORBIT L WELDING M CHINES
AFTER TUBE INSERTION
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AFTERTUBE I NSERTION
TUBE SHEET PROTECTION
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TUBESHEET PROTECTION
Welding parameters for FRONIUS MODEL - FPA 2000
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Welding parameters for FRONIUS MODEL - FPA 2000
Process : GTAW (Automatic )
No of weld passes 1Argon Gas flow rate 4 to 6 ltr /min
Pre Gas time T10 30 SecPost Gas time T11 30 SecPre Fusion current I21 90A
Pre fusion current time T21 0.1Sec
Pulse current I22 90ATime of pulse current T22 100msec
USE OF HYDRAUL IC OPERATED TORQUE CONTROLLED BOLT
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TIGHTNING KIT
OBJECTIVE
To adopt a safe State of the Art methodology in bolt
stretching of coupling bolts of TG Couplings.
GENERAL COUPLINNGS IN TG
HP Tubine to IP Turbine
IP Turbine to LP Turbine
LP Turbine to Generator Shaft
REQUIREMENT
The coupling bolts which are like pins, having a clearance of 0.03mm
diametrically, have to be stretched up to 0.55 mm ,depending on the bolt
dimensions to ensure uniform tightening .
USE OF HYDRAUL IC OPERATED TORQUE CONTROLLED BOLT
G G
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TIGHTNING KIT
Prevalent practice
Nut of the Coupling bolt is tightened by a box spannerLeverage applied on end of the spanner by EOT crane through slings.
Differential expansion monitored by Dial Gauge positioned at bolt ends.
Sources of Error
Dial gauge at the nut end has to be fitted with a long extensionrod,which may lead to error in reading.
Disturbances in the nut also can lead to erratic readings.
Safety element
The whole stretching operation dependent on skill of the Fitter and
EOT Crane operator
Fine movements in EOT Crane not possible
Danger of slipping/shearing always present.
USE OF HYDRAUL IC OPERATED TORQUE CONTROLLED BOLT
TIGHTNING KIT
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TIGHTNING KIT
RECOMMENDATION
Hydraulically operated Torque controlled Bolt tightening kit can be used.
Manufacturing Unit to specify Torque tightening values of individualcouplings.
ADVANTAGES
No error in reading.
Uniformity in bolt stretchingSafe for the working personnel
Safe for the equipment
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IMPROVED PROCESSES
ALL -VOLATI LE & OXYGENATED TREATMENT
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ALL VOLATI LE & OXYGENATED TREATMENT
`
AVT :The basic idea of AVT is to minimize corrosion &erosion corrosion in the low temperature region by
using deaerated high purity water with elevated PH.The actual PH range depend on cycle metallurgy
In absence of Oxygen, the primary reaction of iron
dissolution is inhibited by increasing PH.
The solubility of ferrous hydrazine rises with increasein temperature and then decreases with steep drop to
the solubility of magnetite between 200250 0C. This
results in undesirable magnetite deposit in this
temperature range.
ALL -VOLATI LE & OXYGENATED TREATMENT
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`
To maintain the solubility of ferrous hydroxide in feedwater below or equal to that of magnetite at 250 0C and
to exclude the possibility of over saturation, a minimumPH of 9.6 should be maintained. A PH of 10 would beeven better.
Hydrazine acts both as a O2scavenger & corrosioninhibitor by formation of ferrous oxide hydrate.
OXYGENATED TREATMENT :This process uses oxygenated high purity water tominimize corrosion & erosion corrosion in the feedwater train.
Oxygen, Hydrazine peroxide, air are used as
oxidants
ALL -VOLATI LE & OXYGENATED TREATMENT
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`
Oxygen level should be 30-50 ppb for drum units and 30-
150 ppb for Once Through Units.
Ph level shall be 9-9.6 at Drum units and 8-8.5 for OnceThrough Units
In oxygenated system, p rotective layer consists of
Magnetite(FE3O4) and Hematite(FE2O3) layers
For temperature ranges upto 250 0C the addition ofoxygen allows the formation of oxide protective layer which
have a very low corrosion product release rate in the
following water
ALL -VOLATI LE & OXYGENATED TREATMENT
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ALL VOLATILE TREATMENT (AVT)
Ferrous or mixed feedwater train
Cation conductivity 0.2-0.4 S/cm pH 8.89.6 (Dependent on feedwater metallurgy)
Fe 10ppb N2H4 ( >3x02)
O2 30 ppb )NH3 ( 20 -70 ppb )
OXYGENATED TREATMENT (OT)All ferrous feedwater trainCation conductivity < 0. 15 S /cmpH 8.08.5
HP
HeatersBoiler BFP DA LP Heaters CP CEP CondenserHP
HeatersBFP
LP BYPASS SYSTEM
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LP BYPASS SYSTEM
LP BYPASS SYSTEM
MODIFICATION CARRIED OUT IN OLD LPBPSYSTEM
In case of Turbine trip, direct command will beissued to LP Bypass valves for opening upto 45%for 3 secs.
It is expected that within this 3 secs., the sprayvalves will open and the spray water pressure will beachieved.
However, if the spray water pressure has not
reached a value of 5 kg/cm2 within 3.5 secs., or thecondenser wall temperature has become more than90 0C, the LP Bypass trip command will be issued
LP BYPASS SYSTEM
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SS S S
The sensing of pressure is done by installation ofadditional pressure transmitters at the downstream
of spray water valves The modification was implemented first in
Vindhyachal U#10 and two occasions since themodification, the turbine has tripped and LP Bypassvalves opened within 5 secs thereby saving theboiler trip
LBPB SYSTEM FOR NEW 250 MW SETS
To address this issue, now BHEL, Hwr has gone for
a new High Pressure LP Bypass system which hasmuch better response time. Such system have beensupplied at 1 x 250 MW Parli, 1 x 250 MW Paras, 4 x250 MW JPL and 2 x 250 MW Bhilai sites.
LP BYPASS SYSTEM
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The logic provided for the operation of the LBBypass valves are similar to that of the older low
pressure LPBP valves. However, the following arethe new features of High Pressure LPBP valves
The LPBP valves on sensing increase HRHPressure, automatically opens without looking for
adequate water pressure
For the water injection spray control valves, twocurves have been implemented, one for control andthe other for protection based on down stream
pressure of LPBP valves.
LP BYPASS SYSTEM
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SS S S
If the actual water injection flow is less than flowcorresponding the protection flow, then the LPBP
valves closes on water injection flow protection.
The following problems have been noticed in the newsystem
As per the water injection curve, a continuous waterflow is required to the system which is unnecessaryand wasteful.
The spray water flow element and flow transmitter is
showing 0 reading upto 50% of spray control valveopening.
The problem has been taken up with BHEL, Haridwar
LP BYPASS SYSTEM
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Conclusions :
The new High Pressure system is working satisfactorilyand therefore, the boiler tripping due to reheaterprotection in the new system has been avoided in therecently commissioned units.
By implementing the modification in the old units asdone at NTPC Vindhyachal U#9, 10, the problem of theold units can also be resolved.
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BEST PRACTICES
Best Practices, TSX PSWR
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CARD BOARD BLASTING OF LUB OIL AND CONTROL
OIL LINES OF STEAM TURBINESGENERAL PRACTICE
Only mechanical cleaning is done before start of oil flushing forlub oil and control oil system of steam turbines.
BEST PRACTICE
Exhaustive card board blasting along with mechanical cleaningis carried out for all the control and lub oil system before start ofoil flushing.
This practice is being followed in almost all the sites now.
ADVANTAGES
Effective cleaning and time reduction.
,
Best Practices, TSX PSWR
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USE OF PORTABLE CENTRIFUGE DURING LUB OIL
FLUSHING OF ROTARY MACHINESGENERAL PRACTICE
Generally oil flushing were carried out at ambient temperaturewithout any centrifuging arrangement for rotary machines such
as BFP, ID Fans, FD Fans and Mills.BEST PRACTICE
Oil flushing is carried out with portable oil centrifuge having in-built heating arrangement .
ADVANTAGES
Effective cleaning and time cycle reduction.
,
Best Practices, TSX PSWR
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CHEMICAL CLEANING OF PRE BOILER SYSTEM WITH
CEPGENERAL PRACTICE
Carried out by using temporary pumps, tanks and piping alongwith boiler acid cleaning setup
BEST PRACTICE
Existing CEP and Hotwell are used for the purpose of circulationin the entire system
ADVANTAGE
Effective cleaning of the entire system with minimum number oftemporary loops
Cost and time cycle reduction
Best Practices, TSX PSWR
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USE OF DEAERATOR AS MIXING TANK FOR PRE-
BOILER FLUSHING
GENERAL PRACTICE
Mixing tanks and associated pipings are arranged for carrying
out the pre boiler flushing activities.
BEST PRACTICE
For industrial sets, Deaerator itself is used as mixing tank for
carrying out chemical cleaning of pre-Boiler system.
This results in cost and time cycle reduction.
,
Best Practices, TSX PSWR
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CHEMICAL CLEANING OF BOILER (WW, SH) AND MSLINES IN INDUSTRIAL PROJECTS
GENERAL PRACTICE
Stages are : Alkali boilout, Acid cleaning and passivation
BEST PRACTICE
Alkali flushing, Citric acid cleaning, passivation of the entiresystem
ADVANTAGE
Chemical cleaning activities can be completed even before Boilerlight up
Since both SH and MS lines are acid cleaned & steam blowingcycle is considerably reduced
Cost and time cycle reduction
Best Practices, TSX PSWR
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CHEMICAL CLEANING OF HSD AND NAPHTHA LINES INCCPP
GENERAL PRACTICE
Cleaned by card board blasting
BEST PRACTICE
Citric acid cleaning with passivation
ADVANTAGE
Where the length of HSD and Naphtha lines is more than 500meters cardboard blasting shall not be very effective. Hence,
citric acid cleaning is a most effective way of ensuringcleanliness of the entire piping
Time cycle reduction and trouble free operation
Best Practices, TSX PSWR
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USE OF THERMIC FLUID HEATER FOR COMMISSIONINGACTIVITIES IN GREEN FIELD PROJECTS
GENERAL PRACTICE
Auxiliary boiler is used for generation of steam for pre-
commissioning activities like flushing of Boiler Feed Line,Condensate Lines, Drip Lines etc.
BEST PRACTICE
Thermic fluid heater is used in green field projects in place ofauxiliary boiler for carrying out chemical cleaning activities.
This results in cost and time saving.
Best Practices, TSX PSWR
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ACID CLEANING WITH EDTA
GENERAL PRACTICE
Generally HCL is used for acid cleaning of main boiler.
BEST PRACTICE
HCL is replaced by EDTA for all green field projects especially,where auxiliary steam is not available.
This is safe, environment friendly and reduces time cycle.
Best Practices, TSX PSWR
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PROVISION OF ADDITIONAL INTERSTAGE VALVES FOR
STEAM BLOWINGGENERAL PRACTICE
Interstage valves are not used during steam blowing operationsresulting in three to four days shut down for start of subsequent
steam blowing operations.
BEST PRACTICE
Additional temporary valves are used at Main Steam HP Bypass
lines, CRH Lines during steam blowing operations.
This has resulted in cycle time reduction.
Best Practices, TSX PSWR
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CONTINUOUS STEAM BLOWING IN CCPP
GENERAL PRACTICE
Puffing method is used due to limitation of fuel firing system
BEST PRACTICE
Continuous blowing method (30 minutes) is used in stages
ADVANTAGE
Effective cleaning and time cycle reduction
Best Practices, TSX PSWR
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HIGHER STEAM BLOWING PARAMETERS
GENERAL PRACTICE
Steam blowing is carried out at 40 Kg / sq cm and 300350 deg C
BEST PRACTICE
Steam blowing carried out at 50 Kg / sqcm and 370400 deg C
ADVANTAGE
Effective cleaning due to higher disturbance factor at elevated
parameters Time cycle reduction
Best Practices, TSX PSWR
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USE OF FRESH LUB OIL BOTH FOR FLUSHING AND REUSE
IN ALL INDUSTRIAL SETS
GENERAL PRACTICE
Flushing oil is used for oil flushing operation, fresh oil is used for
normal operationBEST PRACTICE
After cleaning of entire lub oil system by cardboard blasting freshoil is used both for flushing and normal use
ADVANTAGE
Cost and time cycle reduction
Best Practices, TSX PSWR
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AIR LEAK TEST OF LUB OIL, CONTROL OIL, AND
CONTROL FLUID SYSTEM
GENERAL PRACTICE
No separate test conducted before start of flushing resulting inleakage of oil / fluids
BEST PRACTICE
Entire system is pressure tested with compressed air at 5 to 6Kg/sqcm before start of flushing operation
ADVANTAGELeakage of oil and control fluid is minimised
Cost and time cycle reduction
Best Practices, TSX PSWR
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GENERATOR SEAL OIL FLUSHING
GENERAL PRACTICE
Seal oil flushing is done for the site erected pipes upto the inletnozzle in the end shield
BEST PRACTICE
Pre-fabricated pipes from the end shield upto seal ring inlet arealso included in the final stage of flushing.
ADVANTAGEAvoids damage to Generator seal from the entrapped foreignmaterial.
Best Practices, TSX PSWR
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HYDRAULIC TEST OF LUB OIL, CONTROL OIL AND
SEAL OIL LINES
GENERAL PRACTICE
Jacking oil pumps were used for carrying out hydraulic test of luboil, control oil and seal oil line after flushing.
BEST PRACTICE
AC seal oil pimp is used for the purpose of hydraulic test of theabove system.
ADVANTAGEAvoids damage to Jacking oil pumps.
Best Practices, TSX PSWR
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CONDENSER MASS FLUSHING
GENERAL PRACTICE
Cleaning of condenser is normally carried out during steamdumping operation
BEST PRACTICE
Condenser tubes are thoroughly flushed through high pressurejets (fire fighting water) before commissioning of CEP
ADVANTAGE
Duration of steam dumping operation reduced
Cost and time cycle reduction
Best Practices, TSX PSWR
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CLEANING OF VACUUM PUMP SUCTION LINES
GENERAL PRACTICE
No structured cleaning is envisaged except draining the systemthrough drain valves (NB50) during initial commissioning ofvacuum pumps
BEST PRACTICE
Vacuum pumps suction lines are throughly cleaned throughcardboard blasting before commissioning of vacuum pumps
ADVANTAGE
Smooth trouble free operation
Damage of vacuum pumps due to entry of foreign material isavoided
Best Practices, TSX PSWR
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OLTC COMMISSIONING
GENERAL PRACTICE
OLTC is commissioned normally after attaining continuousoperation of unit, i.e., CW system has been put into service forprolonged period
BEST PRACTICE
OLTC is commissioned either
Immediately after running of CW pump or
Before conductance of PG test after thorough cleaning ofcondenser tubes
ADVANTAGE
Collection efficiency of balls increase
Trouble free condenser operation
Best Practices, TSX PSWR
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SELF CONTAINED BEARING COOLING ARRANGEMENTAT EPC PROJECT
GENERAL PRACTICE
Lub oil coolers for ID, FD and PA Fans are kept charged throughthe bearing cooling water system
BEST PRACTICE
In EPC project where due to certain circumstances there is adelay in commissioning of Cooling Water system a separate selfcontained cooling arrangement (Sintex tank, pumps and suitablehoses) to facilitate initial commissioning
ADVANTAGE
Trial operation of all major boiler auxiliaries can be completed bythis method leading to time cycle reduction
Best Practices, TSX PSWR
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PRE ERECTION CHECKING OF BUS-DUCTS
General Practice
Bus-ducts are cleaned and erected
Commissioning jobs taken up later
Best Practice
While at ground, check tightness of all electrical connections ofheaters, thermostats etc
Check heaters healthiness and adjust thermostat tripping pointseasily now
Check drain pad holes before lifting so that any corrections, if
required can now be done easily
Trial assembly of Bus-duct structure on ground before erection
Avoids difficulty in commissioning / troubleshooting
Best Practices, TSX PSWR
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TURBINE X-CRITERIA
General Practice
In X1 criteria for turbine rolling, main steam inlet temperature toturbine has been used for criteria calculation. During any boiler trip
and restart, X1 criteria gets fulfilled even though boiler outlettemperature is less. This leads to cold steam entering the turbine.
.
.Best Practice
Additional criteria X11 introduced using Temperature before HPbypass.
Best Practices, TSX PSWR
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ADDITIONAL TRIPPING DURING ATT
General Practice
Tripping criteria during conductance of ATT does not include manyvital trip inputs
.
.Best Practice
Conditions like MFT, Turbine Bearing temperature VH, axial shift VH,vacuum low, cold gas temp trip, seal oil temp trip etc are added
Best Practices, TSX PSWR
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COMMISSIONING OF ATRS, ATT & AUTOSYNCHRONIZER
General Practice
Normally, ATRS, ATT and Auto-synchroniser are getting commissioned aspending points and not as a part of normal plant commissioning.
So after the pending point is cleared, customer is normally not using the
system.
Best Practice
We are putting efforts for commissioning these system in the first rolling
synchronisation itself.
Recently at Bhilai and Tata Trombay, ATRS and Auto-synchroniser have
been commissioned during first few start-ups.
At Tata Trombay, ATT is also commissioned.
Best Practices, TSX PSWR
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DC EOP AND SOP LATCH RELAY
General Practice
Lub Oil pressure low switch starts DC EOP through max systemSLC latch relay contract..
.
Best Practice
SLC latch relay contract in DC EOP and SOP cabinet looped so thatlub oil pressure low switch contact starts DC EOP and SOP directly,
bypassing MAX system SLC ON. This safeguards machine in the event of AC as well as failure of max
system
Best Practices, TSX PSWR
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AUTOSYNCHRONIZATION
General Practice
As per circuit configuration, auto synchronizer after fulfilling its setcondition directly closes the Generator circuit breaker..
.Best Practice
Additional contact of check synchronization relay wired up in autosynchronization circuit. Here autosynchroniser setting arecoordinated with setting of check synchronizing relay so thatautosynchroniser and check synchronization relay operates at thesame time.
This helps in safeguarding the machine during malfunctioning ofautosynchronizer.
Best Practices, TSX PSWR
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AUTOSYNCHRONIZER TESTING
General Practice
As per normal practice, autosynchronizer is tested and its outputcommand is verified within the panel terminals..
Best Practice
Autosynchronizer is tested in cold condition with supply of PTvoltages through injection kit and actual Generator breaker closing(ensuring that isolators are open)
This helps in optimization of autosynchronizer setting morecorrectly and also total circuit gets checked.
Best Practices, TSX PSWR
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USE OF MULTIPLE FILTRATION MACHINES FORTRANSFORMER DRYOUT
General Practice
One Oil filtering machine (about 6 KL capacity) engaged for dryout
Best Practice More than one such machine put in parallel operation to optimally
utilise transformer drain header flow capacity
Advantage
Cycle time reduced around 50%
Best Practices, TSX PSWR
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TURBINE BEARING METAL TEMPERATURE CHECKING
General Practice
As per normal practice, cabling from bearing metal temperature JBto control room/Cold Junction Compensation(CJC) JB are checked
after installation of thermocouple in bearings...Best Practice
Before installation of thermocouples in bearing, signal upto DCSchecked by heating the thermocouple tag wise.
This ensures correctness of connection, readings and alsoambiguity of polarity change is avoided.
Best Practices, TSX PSWR
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DAVR DUMMY LOAD TESTING
General Practice
As per normal practice, the AVR/DAVR dummy load testing iscarried out at site with the help of 500W lamp or any available
resistive load...Best Practice
Dummy load testing is carried out with same type of resistive load
which is identical in ratio to that of factory testing. With this type oftesting, exact and identical readings with factory can be ensured.
Customer as well as commissioning engineer gets betterconfidence on DAVR working.
Best Practices, TSX PSWR
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PAINTING OF TRANSFORMERS AND BUS-DUCTS
General Practice
Painting works for busducts and transformers are attempted atvery late stages
Becomes difficult because of shutdown requirement and thusopportunity may not be there
Best Practice
At least Station transformer and its busducts may be paintedimmediately after erection completion (before first charging).This transformer hardly goes into shutdown later
Better to paint the other transformers and busducts as well assoon as possible before charging
However, customer opinion / permission may be required sincethey may insist on painting only after all works are completed
Best Practices, TSX PSWR
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SEQUENCE STARTUP OF HT DRIVES
General Practice
All HT drives are generally started individually during firstcommissioning of the drives
This lead to a pending point as we do not get suitable opportunity tocommission the HT drives in sequence mode
Best Practice
All the HT drives to be started in sequence during first startup of the
any HT drive
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Introduction
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Implementation of Best Practices during Overhauling
of T.G. has resulted into the following -
Overhauling cost reduction.
Reduce overhauling periods.
Improvement in quality.
Introduce latest technologies.
Improve customer satisfaction
Implementation of Best practices
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Use of latest technology like induction heating for dismantling andassembly of turbine.
Unit de-synchronization at 480 C of HP shaft temp by decreasingthe load before shut down..
Turbine oil pump stop at 125C (HPS temp).
Barring gear stop at 125C (HPS temp).
To initiate overhauling activities as soon as machine comes tobarring gear.
Decoupling of Generator rotor from turbine rotor and put backturbine rotor in barring.
Start dismantling of generator and O/H activities thereafter.
Review by Site and follow-up from HQ
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Site reviews all activities minutely
Time taking processes, idle times between activities, delay in
arranging spares and mobilization of experts from units etc
are identified well in advance.
HQ also involves in reviewing processes and all important
issues and HQ inputs are duly incorporated on activity
planning at site.
Reduction in overhauling duration to the target schedule is
attributed to meticulously planning and follow-up of critical
activities, which is accomplished in a shortest duration.
Strategic Planning
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List out the History of past problems
Pre-overhaul survey record.
Analyze Present running behavior.
Input from MOUs and utilities.
Timely arrange experts service from MOUs
Milestone based review.
Mobilization of resources 3 days before start of Overhaul.
Scheduling of sequential & parallel activities
Identification of idle time & to avoid them by detailed planning inadvance
All the anticipated spares required for completion of theoverhauling work arranged at T.G. Floor before start of the work.
Generator work starts within 36 hrs of De-synchronization
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0000 hrs : De-synchronization (HP shaft temp at 480 Deg.C)
17.5 hrs : Barring gear stop (HP shaft temp at 400 Deg C)
17.5 hrs. to 20.5 hrs:
AOP stop
Lub o i l to b rg. 5,6,7 blanked & brg . 4 min im ized
LP-Gen coupl ing decoup l ing
Hand barr ing w i l l con t inue dur ing th is per iod
20.5 hrs : B/G re-started
With this practice Generator rotor thread out work startswithin 36 hrs of de-synchronization.
Procedure for decoupl ing of LP-Generator in hot conditions
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Turbine is on Turning Gear. JOP in service, AOP in service.
Loosening of pedestal cover bolts, removal of Vibration probes.
Close turning gear valve to reduce the speed. Simultaneously
loosen and remove pedestal cover bolts.
When Turbine speed becomes zero. Stop AOP while JOP is
continuously kept in service. Continue Hand Barring.
Remove pedestal 4 cover. Close Lubricating oil throttle valve to
the minimum possible.
Simultaneously blank lub oil supply to bearing 5,6 and 7 by putting
gasket in lub oil supply line. (parallel, by 3 gangs). Keep watch on
bearing 1,2 and 3 metal temperature and simultaneously do hand
barring.
Procedure for decoupl ing of LP-Generator in hot conditions
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Put tin sheet/polythene to cover on bearing 4. Start EOP andcontinue hand Barring.
Loosen LP-Generator coupling bolts and decouple LP-generatorby continuing hand barring.
Shift generator rotor away from turbine Stop EOP and Adjust brg. 4lubricating oil throttle valve to normal. Put pedestal cover backand start EOP & barring gear.
Dismantling & prepare for rotor thread out.
At the time of rotor thread out, stop turning gear again and stopEOP. Remove pedestal 4 cover.
After thread out put pedestal 4 cover back. Turbine on Barring
gear with AOP in service till HP shaft temp comes to 125 deg C .
Note: Jacking oil pump is throughout kept in service.
PSWRs Best records on TG overhauls
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Overhauling of IP-LP Turbine & Generator including LP Turbine
blades MPI have been carried out in record lowest time of 8
days barring to barring. (13 days Bar to Bar) on year 2007 at250MW U#2 Dahanu TPS.
Overhauling of LP Turbine & Generator have been carried out in
record lowest time of 9 days barring to barring. (15 days Bar to
Bar) on year 2005 at 250MW U#2 Dahanu TPS . This was achieved
as an exceptional case to avoid power problem in Mumbai.
Overhauling of HP- LP Turbine & Generator including HP rotor
replacement & HP/IP coupling hole reaming, LP free standing
blades MPI & NFT along with bearings 1,2 & 4 replacement have
been carried out in record lowest time of 13 days baring tobarring. (18 days Bar to Bar) on year 2006 at 250MW U#1 Dahanu
TPS.
PSWRs Best records on TG overhauls
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Overhauling of IP-LP Turbine & Generator including LP
Turbine blades MPI & NFT have been carried out in record
lowest time of 12 days barring to barring. (17 days Bar to Bar)in year 2008 at 250MW U#2 Dahanu TPS.
Unit-3 HP Module overhauled in 14 days barring to barring
(19days bar to bar) in year 2006 at 200MW U-3 KSTPS NTPC
Korba.
Capital Overhauling of HP-IP-LP Turbine & Generator
including HP rotor replacement & HP/IP coupling hole reaming,
LP free standing blades MPI & NFT have been carried out in
record lowest time of 35 days barring to barring in year 2008 at500MW U#8 NTPC VSTPS Vindhyachal .
Schedule comparison
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Sl.
No Capacity (MW)
Capital Overhauling TG SET (Barring to Barring)
Previous Best Record Present Record
1 500
(All three module +Gen)
36 Days Unit-6, NTPC,KSTPSKorba on year 1996
35 days Unit-, NTPC, VSTPSVindhyachal on year 2008
2 250(HP-LP&GEN)
30 Days Unit-U-2 REL, DahanuTPS on year 2002
13 days Unit-U-2 REL, DahanuTPS on year 2006
3 250
(IP-LP&GEN)
- 8 days Unit-U-2 REL, DahanuTPS on year 2007
4 200/210
(HP Module)
28 Days Unit-2 NTPC KSTPSon year 2001
15 Days Unit-3 NTPC KSTPSon year 2006
Conclusion
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A benchmark on record minimum duration in KWU design TG setoverhaul could be achieved.
It was the determination, commitment, monitoring and follow-up ofassociated activities that ascertained to achieve a challengingtarget.
Working out activities well in advance with subcontractor
agencies/ partners and round the clock execution of job with newstrategies helped to meet schedule deadlines.
Work can be started as soon as machine comes to Barring gear.
Cooling Down period can be saved relatively by 4 days during the
Generator overhauling.
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IMPROVED SITE FACILITIES
Porta Cabins - to overcome delay in site mobil isation
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Award of Enabling works and its construction takes considerable
time, after receipt of confirm order. This delays posting of site
staff and material management including posting of ConstructionManager.
PSWR has decided to procure Porta Cabins with all amenities as
replacement of Conventional Site office sheds.
This will be provided in all new sites like Satpura, Mauda,Chandrapur, Raigarh, Vindhyachal, Bela Ideal Energy including
all forthcoming sites.
NIT has been floated and tender is likely to be finalized by end
April 2009.
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Porta Cabins - to overcome delay in site mobil isation
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Advantages of Porta Cabins
1. Quick mobilization
2. Quick realization of mobilization advance from customer
3. Quick demobilization
4. Flexibility in use & can be installed as per the site condition
5. Environmental friendly due to cleanness & easy maintenance
6. Provide better facility to site staff
7. Light weight (Easy in handling and transportation)
8. Aesthetic look.
9. Durable and Termite proof
10. Seismic-resistant11. Economical in long term because of repetition
12. Thermal Insulation
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